The present invention relates to an adjusting device, in particular for adjusting motor vehicle seats, comprising a rotatably mounted drive element, a rotatably mounted output element, a first sprag freewheel, by means of which the output element can be blocked in a stepless manner in different positions in both directions of adjustment, and which can be released via a release element, a second sprag freewheel, which is coupled to the first sprag freewheel via the release element and by means of which the output element can be adjusted in a stepless manner into different positions in both directions of adjustment, an actuating element for releasing the second sprag freewheel and an additional locking means for securing the first sprag freewheel against a rotation with at least one rotatably mounted locking lever.
EP 0 979 179 discloses a seat adjuster in which an adjustable part can be blocked in a stepless manner in different positions in both directions of adjustment on a fixed part. By means of a release element the blocking can be released in order to move the adjustable part in both directions in a stepless manner. In order to prevent an adjustment of the sprags during vibrations, an additional locking means is provided with locking levers, which engage in teeth of a gearwheel. However, the illustrated additional locking means must be designed for self-locking in such a way that the distance between the rotational axis of the locking levers and the teeth of the gearwheel is relatively large so that a large installation space is required for the adjustment device. In order to pass the vibratory tests carried out by the manufacturer, however, an adjustment movement must be reliably avoided by means of the additional locking means.